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Procedures for Determining Support of Excavations in Highly Yielding Ground.

Dixon JD; Mahtab MA; Smelser TW
MISSING :19 pages
This Bureau of Mines report describes the results of an investigation for developing and applying procedures for stabilizing excavations openings in highly yielding ground. The approach developed in this report involves nonlinear modeling of the progressive relaxation of the zones of rock mass around the excavations opening where coulomb criterion of failure is exceeded. Stresses are calculated by using a computer code; coulomb-failure condition is examined for both intact rock and joints (using strength parameters 0 and c). The rock mass in the failed zones is relaxed by reducing the young's modulus of the rock based on an empirical formulation that is a function of the shape of the opening and the extent of the failed zone. In addition, the material in the failed zone is assigned reduced strength parameters 0' and c'. The limiting (or convergent) relaxed zone is obtained through an iterative process by manually changing the rock modulus and the strength parameters between iterations. Support pressures are computed by applying forces normal to the excavation surface. The approach is applied to the analysis of stability and support requirements for an entry in a longwall coal mine.
Publication Date
Document Type
IH; Report of Investigations
Fiscal Year
Identifying No.
RI 8990
NIOSH Division
Source Name
Page last reviewed: November 12, 2021
Content source: National Institute for Occupational Safety and Health Education and Information Division